Souper says:

; Function: fn1
%0:i16 = var 
%1:i32 = sext %0
%2:i32 = addnsw 4294902868:i32, %1
%3:i1 = slt 0:i32, %2
cand %3 0:i1

COMMAND: /home/regehr/souper/build/souper -stp-path=/usr/local/bin/stp reduce_298/foo.bc

LLVM says:

define void @fn1() #0 {
entry:
  %0 = load i16* @a, align 2, !tbaa !1
  %conv = sext i16 %0 to i32
  %sub = add nsw i32 %conv, -64428
  %cmp = icmp sgt i32 %sub, 0
  %conv1 = zext i1 %cmp to i32
  store i32 %conv1, i32* @b, align 4, !tbaa !5
  ret void
}

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -c -w -emit-llvm -O3 reduce_298/foo.c -o reduce_298/foo.bc

C source code:

short a;
int b;
void fn1() { b = a - 64428 >= 1; }

x86-64 from LLVM:

fn1:                                    # @fn1
	movswl	a(%rip), %eax
	addl	$-64428, %eax           # imm = 0xFFFFFFFFFFFF0454
	testl	%eax, %eax
	setg	%al
	movzbl	%al, %eax
	movl	%eax, b(%rip)
	retq

COMMAND: /home/regehr/souper/third_party/llvm/Debug/bin/clang -w -O3 reduce_298/foo.c -S -o -

x86-64 from GCC:

fn1:
	movl	$0, b(%rip)
	ret

COMMAND: gcc -w -O3 reduce_298/foo.c -S -o -